EHD kills off record number of Mich. white-tail deer in ’12

The name alone sounds quite alarm­ing — epi­zootic hem­or­rhagic dis­ease. It’s an of­ten le­thal vi­rus that has slammed the Mich­i­gan white-tailed deer herd in 2012, kill­ing an es­ti­mated 10 times as many deer as it has in any other year.

“His­tor­i­cally, this has been a fairly iso­lated dis­ease,” said Tom Coo­ley, a bi­ol­o­gist and pa­thol­o­gist with the Wild­life Dis­ease Lab at the Mich­i­gan Depart­ment of Nat­u­ral Re­sources. “This year, it is much more wide­spread.”

Ar­chery hunt­ers, the first in the woods each deer sea­son, and other vis­i­tors to Mich­i­gan’s out­doors have re­ported about 11,000 cases of white­tails that ap­pear to have died from EHD, in 29 Mich­i­gan coun­ties, as of late last week.

The most se­vere out­break of EHD be­fore this year was in 2010, when an es­ti­mated 1,000 an­i­mals died in just six coun­ties.

EHD is trans­mit­ted by a midge, a gnat-like fly that is found through­out the world and usu­ally in swarms around ponds, lakes, or other wa­ter sources.

In some lo­cales, midges are known as sand gnats, sand flies, or no-see-ums. Once a deer is bit­ten by a midge car­ry­ing the EHD vi­rus, the dis­ease takes its course very quickly.

Within a week, the in­fected deer suf­fers a loss of ap­pe­tite, it seems to aban­don its fear of man, de­vel­ops mouth ul­cers and a high fe­ver, and sal­i­vates ex­ces­sively. The an­i­mal weak­ens rap­idly as it ex­pe­ri­ences se­vere hem­or­rhag­ing.

“This is a fairly fast-act­ing vi­rus,” Coo­ley said. “The deer is usu­ally dead within two weeks.”

White­tails claimed by EHD are of­ten found dead near a source of wa­ter, likely the re­sult of a fu­tile at­tempt to find re­lief from the fe­ver as­so­ci­ated with the dis­ease. EHD is not con­ta­gious within the deer herd, and it does not af­fect hu­mans. There is no sci­en­tific ev­i­dence that hu­mans can pick up the vi­rus from midge bites, or by con­sum­ing ven­ison.

Mich­i­gan’s Io­nia County, lo­cated in the cen­tral part of the Lower Pen­in­sula, be­tween Grand Rap­ids and Flint, has been the hard­est hit by the EHD out­break, with more than 2,000 dead white­tails al­ready re­ported. Coo­ley ex­pects the num­ber of fa­tal­i­ties there and else­where to con­tinue to climb as more hunt­ers are in the field in the com­ing weeks.

“We ask the pub­lic for help on this, to call our of­fices and give us the in­for­ma­tion on where the deer was found, if it was a buck, doe, or fawn, and any other de­tails they can pro­vide,” he said.

“We want to make an as­sess­ment on the im­pact of this dis­ease that is as ac­cu­rate as pos­si­ble, but at this point, no­body re­ally knows for sure. It’s go­ing to be a very in­ter­est­ing fall as we find out what hunt­ers are ac­tu­ally ob­serv­ing out there.”

Coo­ley said there is more than one strain of EHD, and un­less the deer herd has been ex­posed to a spe­cific strain, it has lit­tle built-up re­sis­tance or im­mu­nity to that vi­rus.

“This year, we are likely deal­ing with a pop­u­la­tion of deer that have not been ex­posed to this dis­ease, so no nat­u­ral vac­ci­na­tion has taken place,” he said. “That’s likely why we are see­ing higher mor­tal­ity and mor­bid­ity rates.”

Hem­or­rhagic dis­eases, in­clud­ing EHD, are the most com­mon mal­a­dies af­fect­ing deer in the United States, ac­cord­ing to the Univer­sity of Geor­gia’s South­east­ern Co­op­er­a­tive Wild­life Dis­ease Study. EHD was first iden­ti­fied in New Jer­sey in 1955, and it is a nat­u­rally oc­cur­ring vi­rus that ap­pears to be worse in times of drought.

Coo­ley said the mild win­ter Mich­i­gan ex­pe­ri­enced, fol­lowed by a hot, dry sum­mer, cre­ated near-ideal con­di­tions for the dis­ease-car­ry­ing midges.

Coo­ley said a cou­ple hard frosts usu­ally kill off the vi­rus-car­ry­ing midges, but that some ar­eas in Mich­i­gan have not yet ex­pe­ri­enced those needed cold snaps. He added that he would not ex­pect to see an­other sig­nifi­cant out­break of this strain of EHD next year in the Mich­i­gan white-tailed deer herd, which is es­ti­mated to be about 1 mil­lion an­i­mals.

“Some of the deer will now have an­ti­bod­ies to pro­tect them, and the does will pass on those nat­u­ral an­ti­bod­ies to their fawns,” he said.

The ma­jor­ity of this year’s EHD cases in Mich­i­gan are found in the lower two-thirds of the Lower Pen­in­sula. Cass, Branch, St. Joseph, Hills­dale, and Lenawee coun­ties, which all bor­der Ohio, have had mul­ti­ple lab­o­ra­tory-con­firmed cases of the dis­ease.

Mich­i­gan wild­life bi­ol­o­gists stressed they need the cit­i­zenry to con­tinue to re­port cases of dead deer through the end of the year.

"Some peo­ple may have the per­cep­tion that, once we have con­firmed the pres­ence of EHD in an area, we are no lon­ger in­ter­ested in ad­di­tional re­ports of dead deer in those ar­eas. That is not true. We want the re­ports," Wild­life Divi­sion Chief Russ Ma­son said. "Any and all re­ports, whether the deer seem to have died re­cently or not so re­cently, will help en­sure we have ac­cu­rate in­for­ma­tion about the ex­tent of die-offs."

As of this past week, Ohio has had EHD deaths in its deer herd con­firmed in 19 coun­ties, but the num­bers of white­tails lost to the dis­ease are very low over­all, ac­cord­ing to Mike Tonk­ov­ich, wild­life re­search bi­ol­o­gist with the Ohio Divi­sion of Wild­life.

“In the big pic­ture, EHD hasn’t had a ma­jor im­pact on the deer herd re­gion­ally, but the sit­u­a­tion might be dif­fer­ent lo­cally,” he said “Where the dis­ease oc­curs, the mor­tal­ity rates ap­pear to be very high in that one spe­cific area, but across the land­scape, this has not been a big deal.”

Tonk­ov­ich said EHD has a “very spotty his­tory” in Ohio, with the first con­firmed cases oc­cur­ring in 2002 in Meigs County. He said some deer deaths before that were likely because of EHD. “But we had no idea what it was at the time,” he said. “Con­di­tions cer­tainly point to some of those sus­pi­cious deer deaths in the 1980s be­ing due to EHD.”

Tonk­ov­ich said that there might be a “lin­ger­ing” im­pact from the dis­ease in a few places, but that he be­lieves the “worst is be­hind us.”

“I hope the frost has done its job, and we’ve seen the last of it for this year,” he said.

John Cooper from the On­tario Min­is­try of Nat­u­ral Re­sources Fish and Wild­life Ser­vices in Peter­bor­ough said the prov­ince has seen no in­di­ca­tion of EHD spread­ing from Mich­i­gan to the white-tailed deer pop­u­la­tion in the prov­ince.